Periodontal diseases are inflammatory conditions of the gingival and periodontal tissues ultimately resulting in alveolar bone recession and eventually tooth loss. An accumulation of microbiologic and immunologic evidence suggests an association of one or more gram-negative bacteria with each specific for periodontal disease. Current evidence strongly suggests that Actinobacillus actinomycetemcomitans, a gram-negative bacterium found in subgingival plaque, is associated with the periodontal disease, juvenile periodontitis (JP). JP is a rapidly advancing form of the disease that occurs in children and young adults. The longterm objective is to define if an how A. actinomycetemcomitans causes JP and to develop an immunological approach to the prevention of the condition. The specific objective of this work is to make monoclonal antibodies against specific A. actinomycetemcomitans antigens. These specific immune reagents are then used to identify and characterize the A. actinomycetemcomitans isolates and to study the immunoboiology of the organism. Somatic cell hybridization techniques are used to fuse antigen-sensitized murine splenic cells with a plasmacytoma. Hybridomas synthesizing monoclonal antibodies specific for the bacterial species, serotype, or cell products are identified, cloned and the monoclonal antibody isolated. Monoclonal antibodies and their specific antigens will continue to be characterized and purified respectively. The cross-reactivity of A. actinomycetemcomitans lipopolysaccharides (LPS) with LPS have a variety of other gram-negative subgingival plaque microorganisms will be investigated. Specific, well characterized monoclonal antibodies against A. actinomycetemcomitans will be used to develop methods to directly identify A. actinomycetemcomitans and other organisms from plque samples. In addition, these specific antibodies will be used to identify and localize A. actinomycetemcomitans isolates and the monoclonal antibodies will prove to be of major value in the microbiological and immunological approach to detection, treatment, and prevention of juvenile periodontitis.